Vascularisation for cardiac tissue engineering: the extracellular matrix

Directly coaxial bioprinting of 3D vascularized tissue using novel bioink based on decellularized human amniotic membrane

Despite several progressions in the biofabrication of large-scale engineered tissues, direct biopri nting of perfusable three-dimensional (3D) vasculature remained unaddressed. Developing a feasible method to generate cell-laden thick tissue with an effective vasculature network to deliver oxygen and nutrient is crucial for preventing the formation of necrotic spots and tissue death. In this study, we developed a novel technique to directly bioprint 3D cell-laden prevascularized construct. We developed a novel bioink by mixing decellularized human amniotic membrane (dHAM) and alginate (Alg) in various ratios. The bioink with encapsulated human vein endothelial cells (HUVECs) and a crosslinker, CaCl2, were extruded via sheath and core nozzle respectively to directly bioprint a perfusable 3D vasculature construct. The various concentration of bioink was assessed from several aspects like biocompatibility, porosity, swelling, degradation, and mechanical characteristics, and accordingly, optimized concentration was selected (Alg 4 %w/v - dHAM 0.6 %w/v). Then, the crosslinked bioink without microchannel and the 3D bioprinted construct with various microchannel distances (0, 1.5 mm, 3 mm) were compared. The 3D bioprinted construct with a 1.5 mm microchannels distance demonstrated superiority owing to its 492 ± 18.8 % cell viability within 14 days, excellent tubulogenesis, remarkable expression of VEGFR-2 which play a crucial role in endothelial cell proliferation, migration, and more importantly angiogenesis, and neovascularization. This perfusable bioprinted construct also possess appropriate mechanical stability (32.35 ± 5 kPa Young's modulus) for soft tissue. Taking these advantages into the account, our new bioprinting method possesses a prominent potential for the fabrication of large-scale prevascularized tissue to serve for regenerative medicine applications like implantation, drug-screening platform, and the study of mutation disease.

Application of locally responsive design of biomaterials based on microenvironmental changes in myocardial infarction

Morbidity and mortality caused by acute myocardial infarction (AMI) are on the rise, posing a grave threat to the health of the general population. Up to now, interventional, surgical, and pharmaceutical therapies have been the main treatment methods for AMI. Effective and timely reperfusion therapy decreases mortality, but it cannot stimulate myocardial cell regeneration or reverse ventricular remodeling. Cell therapy, gene therapy, immunotherapy, anti-inflammatory therapy, and several other techniques are utilized by researchers to improve patients' prognosis. In recent years, biomaterials for AMI therapy have become a hot spot in medical care. Biomaterials furnish a microenvironment conducive to cell growth and deliver therapeutic factors that stimulate cell regeneration and differentiation. Biomaterials adapt to the complex microenvironment and respond to changes in local physical and biochemical conditions. Therefore, environmental factors and material properties must be taken into account when designing biomaterials for the treatment of AMI. This article will review the factors that need to be fully considered in the design of biological materials.

F-box and WD repeat domain-containing 7 (FBXW7) mediates the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to affect hypoxic-ischemic brain damage in neonatal rats

The aim of this study was to determine whether F-box and WD repeat domain-containing 7 (FBXW7) can mediate the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to affect neonatal hypoxic-ischemic brain damage (HIBD) in neonatal rats. HIBD rats were treated with LV-shFBXW7. Cerebral infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining, while microvessel density (MVD) was evaluated by immunohistochemistry. Learning and memory were tested using the Morris water maze (MWM) test. FBXW7 and HIF-1α/VEGF signaling pathway proteins were measured by Western blotting. Brain microvascular endothelial cells (BMECs) were isolated to establish an oxygen-glucose deprivation (OGD) model to evaluate treatment with FBXW7 siRNA. Cell viability was detected using a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, while cell migration was evaluated using a wound healing assay. The tube formation of BMECs was also assessed. The results demonstrated that HIBD rats exhibited increased protein expression of FBXW7, HIF-1α, and VEGF. HIBD rats also displayed increased cerebral infarct size, prolonged escape latency and a decreased number of platform crossings. However, HIBD rats treated with LV-shFBXW7 exhibited reversal of these changes. In vitro experiments showed that BMECs in the OGD group had significantly decreased cell viability, shorter vascular lumen length, and shorter migration distance than cells in the control group. Moreover, silencing FBXW7 promoted proliferation, tube formation and migration of BMECs. Taken together, silencing FBXW7 upregulates the HIF-1α/VEGF signaling pathway to promote the angiogenesis of neonatal HIBD rats after brain injury, reducing infarct volume and improving recovery of nerve function in HIBD rats.

Designing of spider silk proteins for human induced pluripotent stem cell-based cardiac tissue engineering

Materials made of recombinant spider silk proteins are promising candidates for cardiac tissue engineering, and their suitability has so far been investigated utilizing primary rat cardiomyocytes. Herein, we expanded the tool box of available spider silk variants and demonstrated for the first time that human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes attach, contract, and respond to pharmacological treatment using phenylephrine and verapamil on explicit spider silk films. The hiPSC-cardiomyocytes contracted for at least 14 days on films made of positively charged engineered Araneus diadematus fibroin 4 (eADF4(κ16)) and three different arginyl-glycyl-aspartic acid (RGD)-tagged spider silk variants (positively or negatively charged and uncharged). Notably, hiPSC-cardiomyocytes exhibited different morphologies depending on the spider silk variant used, with less spreading and being smaller on films made of eADF4(κ16) than on RGD-tagged spider silk films. These results indicate that spider silk engineering is a powerful tool to provide new materials suitable for hiPSC-based cardiac tissue engineering.

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hiPSC-cardiomyocytes attach and contract on positively charged and/or RGD-tagged spider silk variants.

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hiPSC-cardiomyocytes exhibit spider silk variant-dependent morphology upon adhesion.

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Explicit spider silk variants promote long-term contractility of hiPSC-cardiomyocytes.

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hiPSC-cardiomyocytes grown on spider silk materials respond to pharmacological treatment.

Recombinant spider silk protein eADF4(C16)-RGD coatings are suitable for cardiac tissue engineering

Cardiac tissue engineering is a promising approach to treat cardiovascular diseases, which are a major socio-economic burden worldwide. An optimal material for cardiac tissue engineering, allowing cardiomyocyte attachment and exhibiting proper immunocompatibility, biocompatibility and mechanical characteristics, has not yet emerged. An additional challenge is to develop a fabrication method that enables the generation of proper hierarchical structures and constructs with a high density of cardiomyocytes for optimal contractility. Thus, there is a focus on identifying suitable materials for cardiac tissue engineering. Here, we investigated the interaction of neonatal rat heart cells with engineered spider silk protein (eADF4(C16)) tagged with the tripeptide arginyl-glycyl-aspartic acid cell adhesion motif RGD, which can be used as coating, but can also be 3D printed. Cardiomyocytes, fibroblasts, and endothelial cells attached well to eADF4(C16)-RGD coatings, which did not induce hypertrophy in cardiomyocytes, but allowed response to hypertrophic as well as proliferative stimuli. Furthermore, Kymograph and MUSCLEMOTION analyses showed proper cardiomyocyte beating characteristics on spider silk coatings, and cardiomyocytes formed compact cell aggregates, exhibiting markedly higher speed of contraction than cardiomyocyte mono-layers on fibronectin. The results suggest that eADF4(C16)-RGD is a promising material for cardiac tissue engineering.

Preparation of Small-Diameter Tissue-Engineered Vascular Grafts Electrospun from Heparin End-Capped PCL and Evaluation in a Rabbit Carotid Artery Replacement Model

Aiming to construct small diameter (ID <6 mm) off-the-shelf tissue-engineered vascular grafts, the end-group heparinizd poly(ε-caprolactone) (PCL) is synthesized by a three-step process and then electrospun into an inner layer of double-layer vascular scaffolds (DLVSs) showing a hierarchical double distribution of nano- and microfibers. Afterward, PCL without the end-group heparinization is electrospun into an outer layer. A steady release of grafted heparin and the existence of a glycocalyx structure give the grafts anticoagulation activity and the conjugation of heparin also improves hydrophilicity and accelerates degradation of the scaffolds. The DLVSs are evaluated in six rabbits via a carotid artery interpositional model for a period of three months. All the grafts are patent until explantation, and meanwhile smooth endothelialization and fine revascularization are observed in the grafts. The composition of the outer layer of scaffolds exhibits a significant effect on the aneurysm dilation after implantation. Only one aneurysm dilation is detected at two months and no calcification is formed in the follow-up term. How to prevent aneurysms remains a challenging topic.

Functionalization of soft materials for cardiac repair and regeneration

Coronary artery disease is a leading cause of death in developed nations. As the disease progresses, myocardial infarction can occur leaving areas of dead tissue in the heart. To compensate, the body initiates its own repair/regenerative response in an attempt to restore function to the heart. These efforts serve as inspiration to researchers who attempt to capitalize on the natural regenerative processes to further augment repair. Thus far, researchers are exploiting these repair mechanisms in the functionalization of soft materials using a variety of growth factor-, ligand- and peptide-incorporating approaches. The goal of functionalizing soft materials is to best promote and direct the regenerative responses that are needed to restore the heart. This review summarizes the opportunities for the use of functionalized soft materials for cardiac repair and regeneration, and some of the different strategies being developed.

SHCBP1 is a novel target and exhibits tumor‑promoting effects in gastric cancer

The present study investigated the expression and potential influence of SHC SH2 domain-binding protein 1 (SHCBP1) in gastric cancer (GC) cells. SHCBP1 is closely related to cell proliferation and cell cycle progression, but its role in GC remains unclear. The TCGA database revealed that SHCBP1 is highly expressed in GC tissues. Furthermore, SHCBP1 was revealed to be highly expressed in GC cell lines MGC-803 and SGC-7901 cells, and downregulation of SHCBP1 significantly inhibited GC cell proliferation. Furthermore, SHCBP1 expression promoted cell cycle progression and inhibition of apoptosis. Since the CDK4, cyclin D1 and caspase family proteins play important roles in cell cycle and apoptosis regulation, it was examined whether there was an association between SHCBP1 and these signaling pathways in GC. Our results revealed that SHCBP1 promoted cell cycle progression by regulating the CDK4-cyclin D1 cascade and suppressed caspase-3, caspase PARP-dependent apoptotic pathways. Cell invasion and metastasis experiments also revealed that SHCBP1 promoted tumor growth and invasiveness. These tumor-promoting functions of SHCBP1 may provide a potential molecular basis for the diagnosis and targeted therapy of GC.

Cell therapy for heart disease after 15 years: Unmet expectations

Over the past two decades cardiac cell therapy (CCT) has emerged as a promising new strategy to cure heart diseases at high unmet need. Thousands of patients have entered clinical trials for acute or chronic heart conditions testing different cell types, including autologous or allogeneic bone marrow (BM)-derived mononuclear or selected cells, BM- or adipose tissue-derived mesenchymal cells, or cardiac resident progenitors based on their potential ability to regenerate scarred or dysfunctional myocardium. Nowadays, the original enthusiasm surrounding the regenerative medicine field has been cushioned by a cumulative body of evidence indicating an inefficient or modest efficacy of CCT in improving cardiac function, along with the continued lack of indisputable proof for long-term prognostic benefit. In this review, we have firstly comprehensively outlined the positive and negative results of cell therapy studies in patients with acute myocardial infarction, refractory angina and chronic heart failure. Next, we have discussed cell therapy- and patient-related variables (e.g. cell intrinsic and extrinsic characteristics as well as criteria of patient selection and proposed methodologies) that might have dampened the efficacy of past cell therapy trials. Finally, we have addressed critical factors to be considered before embarking on further clinical trials.

Regenerative Medicine Strategies for Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS), the most severe and common form of single ventricle congenital heart lesions, is characterized by hypoplasia of the mitral valve, left ventricle (LV), and all LV outflow structures. While advances in surgical technique and medical management have allowed survival into adulthood, HLHS patients have severe morbidities, decreased quality of life, and a shortened lifespan. The single right ventricle (RV) is especially prone to early failure because of its vulnerability to chronic pressure overload, a mode of failure distinct from ischemic cardiomyopathy encountered in acquired heart disease. As these patients enter early adulthood, an emerging epidemic of RV failure has become evident. Regenerative medicine strategies may help preserve or boost RV function in children and adults with HLHS by promoting angiogenesis and mitigating oxidative stress. Rescuing a RV in decompensated failure may also require the creation of new, functional myocardium. Although considerable hurdles remain before their clinical translation, stem cell therapy and cardiac tissue engineering possess revolutionary potential in the treatment of pediatric and adult patients with HLHS who currently have very limited long-term treatment options.

Position Paper of the European Society of Cardiology Working Group Cellular Biology of the Heart: cell-based therapies for myocardial repair and regeneration in ischemic heart disease and heart failure

Despite improvements in modern cardiovascular therapy, the morbidity and mortality of ischaemic heart disease (IHD) and heart failure (HF) remain significant in Europe and worldwide. Patients with IHD may benefit from therapies that would accelerate natural processes of postnatal collateral vessel formation and/or muscle regeneration. Here, we discuss the use of cells in the context of heart repair, and the most relevant results and current limitations from clinical trials using cell-based therapies to treat IHD and HF. We identify and discuss promising potential new therapeutic strategies that include ex vivo cell-mediated gene therapy, the use of biomaterials and cell-free therapies aimed at increasing the success rates of therapy for IHD and HF. The overall aim of this Position Paper of the ESC Working Group Cellular Biology of the Heart is to provide recommendations on how to improve the therapeutic application of cell-based therapies for cardiac regeneration and repair.

Fabrication and characterisation of biomimetic, electrospun gelatin fibre scaffolds for tunica media-equivalent, tissue engineered vascular grafts

It is increasingly recognised that biomimetic, natural polymers mimicking the extracellular matrix (ECM) have low thrombogenicity and functional motifs that regulate cell-matrix interactions, with these factors being critical for tissue engineered vascular grafts especially grafts of small diameter. Gelatin constitutes a low cost substitute of soluble collagen but gelatin scaffolds so far have shown generally low strength and suture retention strength. In this study, we have devised the fabrication of novel, electrospun, multilayer, gelatin fibre scaffolds, with controlled fibre layer orientation, and optimised gelatin crosslinking to achieve not only compliance equivalent to that of coronary artery but also for the first time strength of the wet tubular acellular scaffold (swollen with absorbed water) same as that of the tunica media of coronary artery in both circumferential and axial directions. Most importantly, for the first time for natural scaffolds and in particular gelatin, high suture retention strength was achieved in the range of 1.8-1.94 N for wet acellular scaffolds, same or better than that for fresh saphenous vein. The study presents the investigations to relate the electrospinning process parameters to the microstructural parameters of the scaffold, which are further related to the mechanical performance data of wet, crosslinked, electrospun scaffolds in both circumferential and axial tubular directions. The scaffolds exhibited excellent performance in human smooth muscle cell (SMC) proliferation, with SMCs seeded on the top surface adhering, elongating and aligning along the local fibres, migrating through the scaffold thickness and populating a transverse distance of 186 μm and 240 μm 9 days post-seeding for scaffolds of initial dry porosity of 74 and 83%, respectively.

Generation and Assessment of Functional Biomaterial Scaffolds for Applications in Cardiovascular Tissue Engineering and Regenerative Medicine

Current clinically applicable tissue and organ replacement therapies are limited in the field of cardiovascular regenerative medicine. The available options do not regenerate damaged tissues and organs, and, in the majority of the cases, show insufficient restoration of tissue function. To date, anticoagulant drug-free heart valve replacements or growing valves for pediatric patients, hemocompatible and thrombus-free vascular substitutes that are smaller than 6 mm, and stem cell-recruiting delivery systems that induce myocardial regeneration are still only visions of researchers and medical professionals worldwide and far from being the standard of clinical treatment. The design of functional off-the-shelf biomaterials as well as automatable and up-scalable biomaterial processing methods are the focus of current research endeavors and of great interest for fields of tissue engineering and regenerative medicine. Here, various approaches that aim to overcome the current limitations are reviewed, focusing on biomaterials design and generation methods for myocardium, heart valves, and blood vessels. Furthermore, novel contact- and marker-free biomaterial and extracellular matrix assessment methods are highlighted.